Conventionally, there have been disclosed and proposed various types of motor drive devices that detect the current flowing through an output stage switching device (a power transistor) and chop the on-period of the switching device so as to keep the current at a predetermined target value (i.e., that have a so-called constant-current chopping capability) (see patent document 1 listed below).
There have also been disclosed and proposed various types of motor drive devices that detect overcurrent resulting from an abnormal state at an output terminal (such as its short-circuiting to the supply voltage) and latch a switching device in an off state when the overcurrent continues beyond a predetermined threshold period (i.e., that have a so-called overcurrent protection capability) (see patent documents 2 and 3 listed below).    Patent document 1: JP-A-H11-206189    Patent document 2: JP-A-H05-111144    Patent document 3: JP-A-H05-111145